Sulfuric-acid process of extracting precious metals from solutions.



UNITED STATES Patented Tune 23, 1903.

ATENT FFICE.

GUSTAVU S A. BAHN, OF AUSTIN,-TEXAS.

SPECIFICATION forming part of Letters Patent No. 731,839, dated June 23,1903.

Application filed November 4, 1902. Serial llo. 130,108. (No specimens.)

To all whom it may concern:

. I designate as the Sulfuric-Acid Process;

andI do hereby declare that the following is a full, clear, and exactdescription of the invention, which will enable others skilled in theartto which. it appertaius to use the Heretofore the precious metals, suchas gold or gold and silver, have been recovered from theiraqueous cyanidsolutions by pass- 1 ing the cyanid solutions containing the preciousmetals through zinc-sponge, zinc-shavings, zinc-granules, agitating withzinc-dust,

by zinc-fumes or zinc-vapors, or by the use of electricity and likemeans.

. The object of my invention is to separate 1 I the precious metals fromtheir cyanid solutions in a rapid and thorough manner and to recover theprecious metals from solutions thereof.

.To carry my invention into effect, I add a quantity of sulfuric acid tothe cyanid solu- .tions containing the precious metals, the

quantity of sulfuric acid varying in volume,

compared with the cyanid solution to be operated on, according to theamount of cyanid i that has beenused in making the solution. Where agreater amount of cyanid has been used ina given quantity of water, agreater volume of sulfuric acid will be required than where a smalleramount of cyanid has been used in the same quantity of water to form thecyanid solution containing the precious metals. I may add the cyanidsolutions containing the precious metals to the sulfuric less than oneper cent. to three per cent. of thecyanid solution to be operated on,ac-

acid, or I may add the sulfuric acid to the cyanid solution containingthe precious metals.

The quantity of sulfuric acid necessary to properly acidulate the cyanidsolution containing the precious metals will vary from cording to theamount of cyanid that has been used in making the solution. Thus where agreater amount of cyanid has been used more sulfuric acid will berequired than where a less amount of cyanid has been used in making thesame quantity of solution to dissolve the precious metals. In measuringthe sulfuric acid I am speaking of it as being measured volumetrically.Thus one per cent. would mean one part, by measure, of sulfuric acid toone hundred parts, by measure, of cyanid solution. Two per cent. wouldmean two parts, by measure, of sulfuric acid to one hundred parts, bymeasure, of the cyanid solution to be operated on. Three per cent. wouldmean three parts, by measure, of sulfuric acid to one hundred parts, bymeasure, of the cyanid solution to be operated on. A larger quantity ofsulfuric acid could be used, but would be less economical. The cyanidsolutions containing the precious metals being acidulated with asufficient quantity of sulfuric acid, I immerse therein a sheet of zinc,although zinc in other form may also be used. Particles of the preciousprecipitate adhering to the zinc may be brushed off and the zincrepeatedly used in other acidulated cyanid solutions so long as any ofthe zinc remains. Chemical action takes place immediately the zinc isimmersed in the properly-acidulated cyanid so lution containing theprecious metals, a part of the zinc being dissolved during the operationand taking the place ofthe precipitated The precious precipitateprecious metals. may now be recovered by means of filtering and meltedor disposed of by other known process. The cyanid solution exhausted ofits precious metals may be regenerated, the zinc recovered, and thecyanid solution again used.

Having fully described my invention, what I claim, and desire to secureby Letters Iatent, is-- 1. The process herein described of precipitatingprecious metals from solutions thereof, which consists in producingcyanid solutions of said precious metals, then acidulating with sulfuricacid said cyanid solutions, then immersing zinc in sheet, plate, orother form, in the acidulated cyanid solution containing the preciousmetals, substantially as set forth.

2. The process herein described of precipitating precious metals fromsolutions thereof,

IO preceding operation, the precious metals, by

u I a 731,839

stantially as set forth.

In testimony whereof I affix my signature, in the presence of twowitnessesfthis 16th day of October, 1902.

G. A. BAHN. Witnesses:

A. E. STEEFOX, O. MANFORT.

filtering'and melting, or other process, sub-

